So far it's cards. I'm going to suggest a variant on an effect I used to do while busking. If you have the World's Greatest Magic: Thumb Tip DVD, you can probably reverse engineer a method on your own.
The magician offers to try something a little unconventional. He requires them both to participate and takes from his pocket a handful of five polished stone rings of the sort used in beaded jewelry, each one a different color. He asks the young lady to pick her favorite. The magician places all five rings in the gentleman's hand and asks him to hold them tightly for a moment. The magician then takes from his pockets a length of thick thread and a coin envelope. He wads up the thread and stuffs it into the envelope, which he then closes. He asks the lady to hold out her hands together, palms up, and places the envelope therein.
He asks the gentleman to hold his closed fist over her hands, look into her eyes, and say her name. Once he says her name, the gentleman is to open his fist and drop the five rings into her hands on top of the envelope. He does so, and when the rings are inspected, one is missing. The one the lady picked as her favorite. The magician removes the four remaining rings and asks the lady to open the envelope. Within, the ring she selected has been strung on the thread, the ends of which are now tied together to make a necklace. The magician tells the gentleman it would only be polite to place the necklace around his lady's neck. He bids them good evening with the necklace as a reminder of the bond between them.